Signal-transmission system



Oct. 19 1926. 1,603,600

R. A. HEISING SIGNAL TRANSMISSION SYSTEM Filed June 28. 1922 PatentedOct. 19, 1926.

UNITED STATES PATENT OFFICE.

RAYMOND A. HEISING, OF MILLBURN, JERSEY, ASSIGNOR T0 WESTERN ELEC- TRIOCOMPANY, INCORPORATED, OF NEW YORK, N. Y., A CORPORATION OF NEW YORK.

Application filed June 28, 1922'.

This invention relates to a method of and apparatus for signaling bymeans of modulated carrier waves.

The object of the invention is to provide apparatus for and methods ofsignaling whereby the same signal can be transmitted through the agencyof two different but simultaneous series of variations in a carriercurrent or elcctron'iagnetic wave.

A further object is to provide apparatus for and methods of producingand transmitting a carrier wave from which the same signal may beproduced by detection in one stage or by detection in successive stages.

A further object is to provide a method of and means for producing ahigh frequency carrier wave, for example, 1,000,000 cycles per second,an intermediate frequency wave, for example 50,000 cycles per secoiu anda signal wave-for example, of speech frequency, the signal wave beingutilized to modulate the intermediate frequency wave and the highfrequency carrier wave being modulated both in accordance with thesignal wave and the modulated intern'iediate frequency wave.

If several transmitting stations in a given locality comprisingapparatus of the kind herein described are operating simultaneously andtransmitting on the same high frequency carrier wave butwith differentintermediate frequencies, a listening station having a single detectorwill hear a confused combination of all of the signals. However,individual stations having suitable arrangements for detecting a pluralnumber .of times and selecting the intermediate frequency cor iespondingto the station from which it is desired to receive signals will be ableto receive from any selected one of the transmitting stations. Asuitable arrangement for doing this would comprise a detector, means forselecting the proper intermediate frequency from the outputlof thedetector, and a second detector for deriving the signal from themodulated wave of intermediate frequency.

The apparatus herein described is illustrative of one form only of theinvention, the novel features of which are defined in the appendedclaims, and may be suitably modifled in various ways as will be obviousto those skilled in the art. Certain features of the system are ofgeneral application.

Serial No. 571,583.

Referring to the drawings, Fig. 1 is a dia gram of a completetransmittin system making use of electric discharge evices in the formof vacuum tubes, and Figs. 2 to 5 inclusive are diagrams of the Waveforms of oscillations existing in different parts of the system.

In Fig. 1 the antenna 1 constitutes an os cillatory or tuned circuitwhich is connected to the anode 2, cathode 3 and control element 4 of ahighly evacuated vessel G- of the audion type by leads 5, 6 and 7respectively. In lead 5 are inductance and capacity elements whichtogether constitute a tuned resonant circuit 10 whose function ishereinafter stated. In lead 7 is located stopping condenser 8. The leakresistance 9 connects the grid and the cathode. Space current for tubeCr and the other tubes hereinafter mentioned is supplied from the battery 11. The elements so far described function to generate highfrequency oscillations i the antenna 1.

A second generating system for generating oscillations of a lowerfrequency, which will be herein referred to as the intermediatefrequency, is constituted by the tube G which has associated therewith atuned circuit comprising variable capacity 12, inductances 13, 1 1 andthe large capacity 15. The usual stopping condenser 16 and highresistance leak path 17 are provided. Capacity 15 and the variableportion of the inductance 14 are coupled to the high frequencygenerating system by suitable connections so that oscillations existingin the intermediate frequency system will cause corresponding potentialvariations between the anode 2 and the cathode 3. Choke coil 18 isdesigned to offer a high impedance to currents of the high frequency anda relatively low impedance tocurrents of the intermediate frequency.Circuit 10 is tuned. to the intermediate frequency and tends to preventoscillations of the intermediate frequency from being impressed upon theantenna.

A vacuum tube V, similar to tubes G and G, has its input circuitcontrolled b a microphone circuit 19 which is connecte to impressvariable potentials of the frequency of sound waves upon the controlelectrode 21 and the cathode 20. These potentials will causecorresponding variations of impedance of the conductive space betweenthe cathode 20 and the anode22. Inductance coil 23 is designed to offera relatively high impedance to currents of the intermediate frequencybut relatively low impedance to currents of speech or audible frequency.Choke coil 24 is designed to offer large impedance tovcur- "entvariations of the frequency of audible Waves.

It will be observed that in the anodecathode circuit of the generator Gwill be high frequency carrier currents, low frequency carrier currentsand speech frequency currents superimposed upon direct current; in theanode-cathode circuit of generator G will be superimposed the samecurrents with the exception of the high frequency carrier currents whichare kept out by choke coil 18. In the anode-cathode circuit of tube Vwill be speech currents superimposed upon direct current. Direct currentonly will flow through the battery 11 as the series of coils 18, 23 and24 will effectually keep all current variations of material magnitudeout of the battery circuit.

In operation, the oscillations of the high and intermediate frequencysystems will e varied in amplitude or modulated in accordance withsounds acting upon the microphone, while the high frequency oscillationswill also be modulated in accordance with the modulated intermediatefrequency oscillations.

The operation of this system may be understood by reference to thediagrams of Figs. 2, 3, 4 and 5. The curves of these diagrams areillustrative only and should not be understood to be exact as to Waveform, phase relationship or relative intensities of the various factorsinvolved, since these will depend upon the particular-value of variousconstants of the system. In Fig. 2, curve a may be assumed to representthe sinusoidal current wave of audible frequenc in Fig. 3, curve 7)represents the unmodu ated oscillations of the intermediate frequency;in Fig. 4, curve 0 represents the modulated intermediate frequenc whoseenvelope (Z is of the frequency and general Wave form of a; and in Fig.5, curve 6 represents the high frequency modulated oscillations in theantenna whose envelope f varies in accordance with the frequencies andwave form of each of the curves at and c. If electric currents of thetype illustrated by curve 6 be detected, the output of the detector willcontain a current component represented by curve a and another componentrepresented by curve 0. If the-first of these components be disregardedand the second he again detected, a component corresponding to the curvea will again be obtained in the output of the Second detector.

While described as a radio transmitting system, this system may beadapted for use with a suitable conductive line connecting it with oneor more receiving stations, as for example, by substitutin a tunedcircuit for the antenna 1 and coup in the line thereto.

Itis within the scope o the invention to modulate by varying, at anydesired stage, the amplitude, frequency, or other characteristic, or acombination of characteristics of the wave to be acted upon, or bygenerating a wave having the desired varying characteristic orcharacteristics.

The subject matter hereinafter claimed comprises a portion of thesubject matter of applicants application Serial No. 272,153, filedJanuary 20, 1919, which has been abandoned.

What is claimed is:

1. In combination, an electron discharge device, means whereby saiddevice functions as an oscillation generator, a second electrondischarge device, means whereby the second device functions as agenerator of oscillations of a frequency different than that of saidfirst mentioned device, a third electron discharge device, means forcausing current variations therethrough' at a rate different from thefrequency of either of said generators, and a coinmon constant currentsource for supplying space current to said dis charge devices.

2. In combination, a high frequency oscillation generating system, anintermediate frequency oscillation generating system coupled theretofor. causing variations of amplitude in the high frequency oscillationsgenerated, means for reducing the reaction of the first system upon thesecond, a lower frequency variation producing system cou pled to thefirst and second systems for causing variations in amplitude of theirgenerated oscillations, and means for reducing the reaction of thesecond system upon the third.

3. In combination, a space discharge de vice having an anode, a cathodeand an impedance-varying element, a second space dis charge devicehaving an anode, a cathode and an in'ipedance-varying element, a thirdspace discharge device having an anode, a cathode and animpedance-varying element, means whereby the first of said devicescauses a variation in voltage between the anode and the cathode of thesecond and third, and means whereby the second causes variations ofvoltage between the anode and the cathode of the third.

4. In combination, a tuned circuit, a vacuum tube device including ananode, acathode and an impedance-varying element for generatingoscillations in said circuit, asecond tuned circuit, a second vacuumtube device including an anode, a cathode and an impedance-varyingelement for generating oscillations in said second circuit, said secondcircuit being coupled to a circuit including a conductive space of saidfirst mentioned vacuum tube device, a microphone controlled vacuum tubedevice and output circuit therefor, means for coupling the said outputcircuit to a circuit including a conductive space of said firstmentioned vacuum tube'device, and a common source of space current forsaid devices.

5. An energy transforming system comprising more than two electrondischarge systems, input circuits individual to said systems, means forapplying voltages of different frequencies to the respective inputcircuits, means for supplying space currents to said systems andmaintaining the sum thereof substantially constant, and output means forutilizing the energy transformed by said transforming system.

6. A system comprising a thermionic generator of oscillations, a sourceof modulating waves for said generator, and a modulating devicecontrolled thereby, a portion of the circuit of said generator being incircuit with said source and in circuit with said device.

7. A system comprising a space discharge device, a source, of waves tocontrol said device, an amplitude varying device controlled by saiddischarge device, and a circuit connected between two electrodes of saidspace discharge device having a portion in common with circuitsincluding said source and said amplitude varying device respectively.

8. A system comprising a space discharge device having an externalcircuit, a controlling device therefor, and a device controlled thereby,a portion of said circuit being in common to circuits including saidlast mentioned devices respectively.

9. A system comprising three devices which function respectively asfirst, second and third sources of waves. of different frequencies,means functioning in cooperation with said second device whereby thewaves produced by it are varied in accordance with the waves produced bythe first device, and means functioning in cooperation with said thirddevice whereby the waves produced by it are varied in accordance withthe varied waves produced by said second device and but one of theremaining devices, and so on to the last device of the series from whichall but the lowest frequency variations are excluded, in combinationwith means whereby one of said devices is caused. to support currentvariations of all the frequencies.

11. A system in, accordance with claim 10 in combination with a sourceof discharge current for all said devices.

12. A radio system comprising sources of low frequency current,intermediate frequency current and high frequency current in combinationwith three choke coils arranged in series, each of said coilsbeingdesigned to offer high impedance to a range of frequenciesincluding the frequency of one of said sources and a relatively lowimpedance to ranges of frequencies including the frequency of such ofthe said sources as are of lower value.

13. A circuit for use in signaling systems whereupon voltages of atleast three frequencies are impressed, comprising at least three sets"of conductively connected apparatus, impedance means included in saidcircuit whereby one set is limited to supporting currents of only one ofsaid frequencies, impedance means functioning in cooperation withsaidfirst named impedance means whereby the second set is limited tosupporting currents of that frequency and the next higher frequency, andmeans whereby the third set supports currents of all three frequencies.

In witness whereof, I hereunto subscribe my name this 27th day of June,A. D. 1922.

RAYMOND A. HEISING.

